Nd apparatus for heat-sealing paperboard package closure flaps

ABSTRACT

Method and apparatus for heat-sealing paperboard package closure flaps having a heat sealable coating. While the package moves, two flaps are brought into proximity along two planes diverging at an acute angle, and upon the facing flap surfaces, are impinged one or more high-volume, low-velocity streams of very hot air, each along a controlled narrow area to heat one or more critical strips of each flap above the heat-sealing temperature. Immediately thereafter, the flaps are forced together and held together while they are cooled, until the lowering of the temperature results in completion of the seal.

United States Patent [1 1 Howe [ METHOD AND APPARATUS FOR HEAT-SEALINGPAPERBOARD PACKAGE CLOSURE FLAPS [75] Inventor: William J. Howe, LosAltos, Calif.

[73] Assignee: Georgia-Pacific Corporation,

Portland, Oreg.

[21] Appl. No.: 273,945

Related U.S. Application Data [63] Continuation of Ser. No. 101,126,Dec. 23, 1970, abandoned, which is a continuation-in-part of Ser. No.696,794, Jan. 10, 1968, abandoned.

[52] U.S. Cl 53/47, 53/375, 53/388 [51] Int. Cl B65b 7/20 [58] Field ofSearch 53/47, 375, 388

[56] References Cited UNITED STATES PATENTS 3,462,916 8/1969 Chin 53/375Dec. 11, 1973 2,155,614 4/1939 Petskeyes et al. 53/388 X 3,340,7779/1967 l-littenberger et al... 53/375 X 3,535,987 1/1970 Schafer et a153/375 X Primary Examiner-Travis S. McGchee Attorney-Robert Wickersham[57] ABSTRACT Method and apparatus for heat-sealing paperboard packageclosure flaps having a heat scalable coating. While the package moves,two flaps are brought into proximity along two planes diverging at anacute angle, and upon the facing flap surfaces, are impinged one or morehigh-volume, low-velocity streams of very hot air, each along acontrolled narrow area to heat one or more critical strips of each flapabove the heatsealing temperature. Immediately thereafter, the flaps areforced together and held together while they are cooled, until thelowering of the temperature results in completion of the seal.

19 Claims, 16 Drawing Figures PAIENIEDIIEI I I Isrs SHEET 10F 3 AMBIENTAIR I 7 I l I 3; l I I AMBIENT AIR mmmmmm 1 I1 mm mm INVENTOR WILLIAM J.HOWE FlG 7 FIG-8 0W, MMQMJM ATTORNEYS PAIENIEDUEC 1 1 1923 3,777,448

v 329 INVENTOR. E WILLIAM J. HOWE |=|c-s 1o 322. 0M,

ATTORNEYS PAIH-HHHIEL H mm 3.777.448

SHEET 30? 3 7 lOl AB 77 I02 F iG 13 INVENTOR. "4 WILLIAM J. HOWE F I GATTORNEYS METHOD AND APPARATUS FOR HEAT-SEALING PAPERBOARD PACKAGECLOSURE FLAPS This is a continuation of application Ser. No. 101,126,filed Dec. 23, 1970, now abandoned which in turn is acontinuation-in-part of application Ser. No. 696,794, filed Jan. 10,1968 also abandoned.

This invention relates to improvements in method and apparatus forheat-sealing paperboard packages and the like. It also relates to somesubcombinations, including a novel heating apparatus, a novel manifoldfor emitting hot air against a pair of package flaps that are to besealed together, and a novel closure means.

Paperboard packages often have their flaps provided with heat-scalable(usually thermoplastic) coatings which are heated, and then the packageis closed and sealed by forcing the heated flaps together and holdingthem together until the heat scalable material is cooled sufficiently toprovide a tight seal. Heretofore, there have been difficulties inaccomplishing this heat-sealing operation efficiently without damagingthe carton or marring its outside surface coating, and, as a result,apparatus for accomplishing it automatically has tended to be veryexpensive. Also, when packaging frozen goods, it has often beendifficult to employ heat sealing without damaging the goods themselvesby subjecting them to too much heat. Further, prior-art apparatus is notreadily adjustable to changes in types of coatings or to speed changesin packaging machinery. A feature of the present invention is thatrelatively simple apparatus costing only about one-tenth orone-twentiety as much as comparable prior-art apparatus can do the jobefficiently and well, without any damage to the frozen contents insidethe package or to the package itself, and can do so in a very simple andfoolproof manner. Installation costs and maintenance costs are muchlower, too, and changes in coating types or in the speed of thepackaging machinery are readily made.

Some of the better prior-art systems have required special air driersfor drying the air before it is heated, because moist air damages theirheater elements, and they have required a supplemental air-compressorsystem in addition to the normal compressed air system of the packagingplant. The present invention operates without any special driers anduses normal plant compressed air. No supplemental system is needed. Infact, my new system uses much less air than do the prior-art systems. 4

An important feature of the invention is the provision of a manifold andheater system in which heated air at high temperature is evenlydistributed at low-velocity and high-volume over a relatively shortdistance to quickly heat the plastic coating on the flaps to thetemperature at which it becomes tacky or otherwise heat sealable. Thepresent invention does this in a single manifold without necessarilyhaving separate compartments in the manifold. An even flow of airthroughout the manifold is provided by spacing the discharge holes tobalance the naturally uneven input to those holes. At the holes, themanifold is independently positioned away from the flaps to enable flowof air. Also, by using separately controlled multiple heaters the system(with or without a partition in the manifold) can be used to provide adifferent temperature at one end or one portion of the manifold than atanother end or portion thereof for quick adaptability to various coatingtypes and machine speeds.

The heater housings of the invention prewarm and predry ambient airwithout any supplemental warmers or driers being required, and theyprovide a swirl-type of air flow through the double jacket in the firsttwo of the three passes through the heater, thereby getting the greatestefficiency inair heating. Also, less heat is lost between the heatersdischarge into the manifold and the manifold discharge than is lost inconventional apparatus, partly because the outlet from the heaterelements is large and located quite close to the manifolds dischargeopenings and partly because of the low velocity of the heated air, amajor feature of this system. As a result, the device uses-less wattagethan conventional systems and wastes less heat.

in this invention no insulation of any kind is needed over or around theheater housings, yet their outer walls are actually barely warm to thetouch, although extremely hot air (typically 1000F. to 1200F) is sentfrom the heaters into the manifolds. It is the only system in use todaywithout insulation.

Another feature of the invention is that the air stream flow from themanifolds is designed to contact the flaps only where it is needed andnot over their full surfaces. The low velocity of the air stream helpshere. The flaps do not touch the manifold while they are being heated,and when they are being cooled, they do not require back-up pressure.

This invention employs much less air than conventional systems and usesit efficiently at the flaps and at low velocity; so it does not inflatethe packages, as do many prior-art systems, and as a result, there is notime and space wasted in waiting for packages to deflate before packingthem in cases. Also, no temperature correction of the product isnecessary and there is no product deterioration.

Another feature of the invention is its mechanical closure. Closing ofthe outer major flaps is achieved within about one inch from thedischarge edge of the manifold, and all of the holding needed to assurecompletion of the seal takes up only about two feet, even for quiterapidly moving packages, i.e., up to feet per minuteQNo support isneeded, even when sealing polyethylene to polyethylene. Packagedistortion is eliminated by special apparatus. The type of compressionemployed in the holding section eliminates the requirement of any kindof refrigerant; instead, free running rollers do the compression whilean air stream of ambient air is directed against the carton flaps androllers. This system can also be used in connection with folder-gluersof a heat-sealing type in a manufacturing converting plant.

To summarize the invention briefly, the apparatus includes a hot airmanifold having two surfaces meeting at a sharp acute angle, each suchsurface having at least one row of openings along it for emitting theheated air. These openings are positioned away from the flaps, so thatthe air can move away. A novel air heater connected to the manifoldcomprises a long slim cylindrical ceramic heater with a plurality ofcircumferentially spaced long air passages, an inner shell surroundingand against the outer wall of the ceramic heater. Around the inner shelland spaced from it to provide a passage is an'intermediate shell, and anouter housing surrounds the intermediate shell and is spaced from it toprovide a passage, this outer housing has a tangential air inlet. Hence,the air gets three passages through the heater. The ends of theintermediate shell and outer housing are closed, while the ceramicheater is connected directly to the manifold at one end and is spaced atits other end from the closed end of the intermediate shell. Theintermediate shell has aperture means at the end opposite the inlet, sothat air entering the tangential inlet is swirled between the outerhousing and the intermediate shell for its first passage, then goesthrough the aperture in the intermediate shell and is swirled around theinner shell in its second passage, goes through the heating passages inthe ceramic heater for its third passage, and then enters the manifoldthrough a large outlet. At the manifold the outlet holes are so spacedthat the air flow is longitudinally even, and the area of the air flowis balanced to the area of the inlet so that no excess pressure isgenerated by the expansion of heated air and so that the outlet holessupply the air at the same low velocity as that of the entering air.

Suitable plows, completely independent of the manifold but adjustablerelative to it, push the flaps to the proper position relative to themanifold. The positioning of the flaps independent of any guides on themanifold makes this system different from other heretofore known andeliminates dependency on any such manifold-mounted guides to positionthe flaps. This system enables adjustability to accommodate variouscoatings, carton velocities, and air temperatures without changing anyof the parts. There are no fixed guide bars nor any other inflexiblepositioning pieces. Thus, the heated flaps are forced against eachother, preferably by a set of three free-running rollers, which assureproper positioning of the flaps, along with squareness of the carton andproper dimensioning. The flaps are then held together by one or morerows of cylindrical rollers while cooling air is directed down at theflaps, between the rollers.

Other objects and advantages of the invention will appear from thefollowing description of some preferred embodiments.

In the drawings:

FIG. 1 is a fragmentary top plan view of a package closure system ofthis invention, including a conveyor system along which paperboardcartons (which may contain frozen food or any other contents) are movedthrough the flap-heating and heat-sealing stages, which embody theprinciples of the invention.

FIG. 2 is an enlarged view in section taken along the line 22 in FIG. 1.

FIG. 3 is an enlarged view in section taken along line 33 in FIG. 1.

FIG. 4 is an enlarged view in side elevation taken along the line 44 inFIG. 1.

FIG. 5 is a view in section taken along the line 5-5 in FIG. 4.

FIG. 6 is a view of a portion of FIG. 5, shown with holding rollersbearing against the outer major carton flaps to hold it closed againstthe inner major flap, during cooling and congealing of the heat-sealingcoating.

FIG. 7 is an enlarged view in elevation and in section taken along theline 77 in FIG. 1 showing the air heating of the coating on the outermajor and inner major flaps by a manifold of this invention.

FIG. 8 is an enlarged view taken in section along the line 88 in FIG. 1,showing closure of the heated flaps of FIG. 7.

FIG. 9 is a view taken along the line 99 in FIG. 2, showing thestructure'of the air heater.

the

FIG. 10 is a view in perspective of a double manifold unit of theinvention, used for closure of wide flap systems with overlap.

FIG. 11 is a fragmentary view in section taken along the line 1l-II inFIG. 10.

FIG. 12 is a fragmentary view in section of a modified form of manifoldalso embodying the principles of the invention, employing a somewhatdifferent shape and two double rows of discharge openings.

FIG. 13 is a view similar to FIG. 5 of closing rollers for use with themanifold of FIG. 12.

FIG. 14 is a similar view of another form of closure device for hearingon four areas of the closure flaps.

FIG. 15 is a front elevational view of another modified form of manifoldhaving slots and flow-enabling recesses, with a portion cut away to showthe rear wall.

FIG. 16 is an enlarged fragmentary view in section taken along the linel6-16 in FIG. 15.

As shown in FIG. I, l, a paperboard carton 20 is moved along a conveyor21. The carton 20 has outer major flaps 22 and 22a and inner major flaps23 and 23a. These flaps 22, 22a and 23, 23a are to be closed againsteach other and sealed. At least one of the flaps 22 and 23 has beencoated on one of the two facing surfaces 24 and 25 (FIG. 7) with asuitable thermoplastic or other material enabling heat sealing. Oftenboth flaps are so coated. For example only, a frozen food product, suchas a pie, may have been placed inside the carton 20, and the operationis to be conducted without in any way overheating that frozen foodproduct or marring the outer surface of the carton. On each side of thepackage, the closure is to be accomplished simultaneously, in order tomaintain alignment of the carton 20, so that there are duplicateapparatus, one on each side of the conveyor 21, comprising identicalflapheating units 26 and 27 and identical flap-closing units 28 and 29.

A narrow plow 30 precedes each heating unit 26 and 27 and bends theinner major flap 23 up to perpendicular position at the end of thecarton 20, and a rod plow 31 then bends the outer major flap 22 over toa suitable acute angle, as shown in FIG. 7, as the carton 20 approachesthe heating unit 26 or 27.

The plows 30 and 31 immediately precede and continue alongside of amanifold 32 and are made so that they correctly position the flaps 22and 23 but are not themselves subject to heat build-up when no carton isrunning through the machine; they stay cool while the machine runsempty. The manifold 32 is a very important element of each heating unit26, 27 of the invention, and each manifold 32 is provided with at leastone or more heaters; in the embodiment shown in the drawings there are apair of such heaters 33 and 34. The manifold 32 emits very hot (e.g.,I000 to I200F.) air at high volume and at low velocity; this air heatsthe plastic coating of certain narrow areas on the flaps 22 and 23 abovethe temperature where the coating becomes tacky, and then the outermajor flap 22 is closed against the inner major flap 23 by a closingroller 35 or a plow and is held closed against it under pressure by theclosure system 28 M29, while cool air is blown against the carton 20 andflaps 22 and 23 from a coolair manifold 36. All these will be nowdiscussed in more detail.

In the form of the invention shown in FIGS. 1-11 each hot-air manifold32 is provided with two walls and 41 meeting at a vertex 42 of a sharpacute angle.

This makes it possible to bring the flap 22 close to the flap 23 at themanifold 32. Each wall 40 and 41 is provided at suitable locations witha row of discharge openings 43 and 44 at different distances from thevertex 42 and not opposite each other, to assure correct overlap of theheated areas in the flaps. As shown in FIGS. 2 and 7, the heated airthrough the openings 43 and 44 is directed against the flaps 22 and 23,the inner major flap 23 being perpendicular to its main carton walls,while the outer major flap 22 is at an acute angle, as set by the plow31 and held in position, as by a rod 37, the resistance of the flap 22to folding keeps it against the rod 37 without any spacing member havingto be between the flaps 22 and 23. The manifold 32 may be generallytriangular in cross section, as shown in FIGS. 2 and 7, with a thirdgenerally vertical wall 45 provided with one or more openings 46 and 47to receive the output from the heater units 33 and 34; in this instancetwo heater units 33 and 34 are shown, but

there may be only one heater or theremay be more than two. The length ofthe manifold 32 depends partly on the number of heaters and partly onthe speed of the conveyor. For packaging closure it may be about 3 to 8inches long, typically, but may be longer; for providing a manufacturersjoint at very high speeds, it may be a couple of feet long, e.g., 16 to48 inches long for a speed of 1200 feet per minute.

As shown in FIG. 3, the openings 43 leading from the manifold 32 arespaced apart, not evenly but in a pattern which gives an evendistribution of the discharge air, and the openings 44 are similarlyspaced, so that the container flaps 22 and 23 are properly heated withina very short travel, a few inches travel only. As shown in FIG. 7, themanifold walls 40 and 41 are spaced from and lie at an angle to the flapsurfaces 24 and which they are to heat, thereby spacing the manifoldfrom the flap surface 25 in the vicinity of the openings 44, to enableflow of air, and only a small area 48, 49 of each flap surface 24, 25 isheated. The total area of the openings 43 and 44 is made sufficient togive high-volume, low-velocity air flow, so that the hot air impingesagainst the flap surfaces 43, 44 to heat them without causing highvelocity in toward the vertex 42 and sending air into the inside of thepackage being closed. Also, the openings 43 and 44 are not spaced thesame distance from the vertex 42 but are instead spaced to impinge withflaps at areas 48 and 49 that lie at the same distance from where theflaps 23 and 24 meet; this means that the openings 43 lie closer to thevertex 42 than do the openings 44, and it means that very narrow areas48 and 49 can be heated and the heat confined to them, since they willmate accurately.

As shown especially in FIGS. 2, 3, and 9, each heater unit 33 or 34comprises an outer metal housing 50, an intermediate metal shell 51, anda ceramic heater 52 with a close-fitting metal inner shell 53 around theouter circumference of the heater 52. The housing 50, intermediate shell51, and inner shell 52 are all cylindrical tubes and are radially spacedfrom each other to provide cylindrical annular passages 54 and 55 oneach side of the intermediate shell 51. The outer housing 50 is providedwith an inlet 56 leading generally tangentially into it adjacent the enddistant from the manifold 32, to induce swirling of the air around theintermediate shell 51. A suitable air supply tube 57 supplies ambientair under low pressure to the inlet 56. A pair of end closure members 58and 59 connect the outer housing 50 to the intermediate shell 51, themember 58 closer to the manifold 32 being also used to provide spacing,not only between the intermediate shell 51 and housing 50 but alsobetween the intermediate shell 51 and the inner shell 52 andalso aconnection fitting 60 to the manifold opening 46 or 47. The intermediateshell 51 is thus fully supported at both ends, to maintain accuratespacing and prevent movement during operation, and it is provided withan outer end closure mcmber 61 through which may extend an electricalpower line 62 for the heater 53. The ceramicmember 53 and its outersheath, the shell 52, is held and spaced away from the intermediateshell 51 by the member 58 and by spacing and supporting screws 63. Thus,there is an outer swirl passage 54 between the housing 50 and the shell51, an inner swirl passage 55 between the shell 51 and the shell 52, andthere is a plurality of straight-flow passages 64, each containing ahelical heater element 65, running through the ceramic heater 53. Theheating elements 65 extend the length of the ceramic body 53, andprovide intense air heating for the air passing through the passages 64,which are the only airflow passages through the heater 53. What appearsto be a cylindrical passage 66 is blocked intentionally and merelyserves to lessen the amount of ceramic body.

As a result of this structure, air enters tangentially through the inlet56 and swirls around in the first passage 54, going toward the manifold32. Near the end wall 58 closest to the manifold 32 it passes through aslot or other aperture or apertures 67 in the shell 51 and then swirlsback inside the second passage 55 to the opposite end 61 most distancefrom the manifold 32. Then it turns in and goes by the space 68 inthrough the plurality of third passages 64 and from there directly intothe manifold 32 through the opening 47, which is the full size of theheater 53, so that there is no restriction between the heater 53 and themanifold 32 but rather an enlargement there. In the manifold 32 it goesup and goes out the two series of discharge openings 43 and 44 impingingupon the thermoplastic coated flaps 22 and 23 as shown in FIG. 7. Theaccumulated total of the areas of the openings 43 and 44 in the manifold32 is about ll()% of the accumulated open cross-sectional area of thepassages 64 through the heater 53. This enables a rise in ambient airtemperature to about 1000F. to l 150F. to take place without increasingthe velocity of the heated air. The purpose is to send a volume of hotair at low velocity through the openings 43 and 44 and against the areas48 and 49, rather than to send high-velocity air through them withresultant forcing of the air to unwanted places and and unwantedrapidity in the cooling of the air. The velocity of the air issuing fromthe openings 43 and 44 is actually lower than that going into the inlet56. It has been found that this system heats the flaps 22 and 23 quiterapidly to a temperature enabling their closing. Therefore, such amanifold 32 need only be a few inches long. Most of the housing 50 ismerely warm to the touch, though the air inside is rapidly dried andheated and may emerge from the heater 33, 34 at temperatures up tolO0O-1200F., for example.

Right beyond the end of the manifold 32 are the closing rollers, whichpreferably comprise a pair of hemispherical rollers 70 and 71 contactingthe opposite faces of the carton 20, as shown in FIGS. 4 and 8, and thehemispherical roller 35, which engages the outer major flap 22 andcloses it against the inner major flap 23. While the hemispherical shapeis preferred, it is not essential in all cases. The low-friction roller35 is mounted with its flat portion 72 parallel to the main walls of thecarton 20 and perpendicular to the flap 23. The other rollers 70 and 71are mounted perpendicular to this roller 35 and engage the walls 73 and74 of the carton 20, retaining the cartons shape and squareness whilethe flap 22 is pushed against the flap 23', these rollers 70 and 71serve no other purpose than the prevention of distortion of the cartonfrom friction of the closing roller 35; they, thus, insure that the edgeof the flap 22 seals parallel to the score line of the flap 23.

Just beyond the closing rollers 35, 70, and 71 are the hold-down rollersystems 28 and 29, each of which in the illustrated embodiment comprisestwo staggered rows of cylindrical rollers 75 and 76 and mounted to befree running and to engage the carton 20 as the carton 20 is moved alongthem by the conveyor 21. They provide sufficient pressure for retainingthe closure without putting so much pressure that it becomes difficultto move the carton 20. They do not seal the carton; they retain theflaps in their closed position while they cool and seal themselves.These rollers 75 and 76 are adjustably mounted, as shown in FIG. 5,between a lower plate 77, which holds the shaft 78 for the lower roller76, and an upper manifold 36 which holds the shaft 79 for the upperroller 75, the plate 77, the manifold 36 and plate 77 being heldtogether by a bolt 80 and spaced apart by a spacer 81 which may bechanged to give different spacing. The manifold 36 has an inlet 82 for asupply of cold air, which can be simply ambient atmospheric air, and isprovided with a series of discharge openings 83 in a face 84, which aremade to point down against the carton 20 at approximately the levelwhere the horizontal faces meet the convex faces of the roller 70 and71. By this means, the carton flaps 22 and 23 are rapidly cooled, and inonly about two feet the carton can be released from the rollers 75 and76, and it will remain tightly closed without any additional pressurebeing necessary.

As shown in FIGS. and 11, the system may be applied as well to a systemhaving two outer flaps which overlap by using a staggered pair ofmanifolds 32 and 32a each with their heaters. First one outer flap issealed and then the other.

FIG. 12 shows a modified form of manifold 90 with a rhomboidal shape,having a vertical wall 91 meeting an inclined upper wall 92, a rearvertical wall 93 and a lower inclined wall 94. This shape is oftendesirable, and for purposes of example is shown with two rows ofdischarge openings on each of the two upper walls openings 95 and 96 inthe wall 91 and openings 97 and 98 in the wall 92. There could, ofcourse, be single matched rows of openings or more than two rows perwall. The rows are, of course, matched to cause the impinged surfaces tomeet when the flaps are closed. Two rows of openings enable more sealingarea and sealing strength than does one row. Double rows are notgenerally practical with the manifold 32, for the divergency betweenrows would render the two rows different in the temperatures theyimpart. The rhomboidal shape does enable this, and positive spacing maybe obtained by rods 99 and 37, that enable air flow, which are notmounted on the manifold but beside it, to enable free adjustmentrelative to the manifold.

With double rows of discharge openings, as in FIG. 12, the holdingassemblies 28 and 29 are preferably modified as shown in FIG. 13 toreplace the bolt and spacer 81 with a longer bolt 100 and a large spacer101.

With even wider flaps and more rows of sealing plastic, the structure ofFIG. 14 may be used, with a bolt 102 and a bar 103 inserted between twospacers 104 and 105 and supporting on shafts additional rollers 106 and107. Many other modifications are possible.

The manifold may be varied in many ways. A manifold 110 is shown inFIGS. 15 and 16. It may have the rhomboidal shape of the manifold 90 buthas vertical slits 111 instead of double rows of openings to heat a wideband on the flaps. This wider hot-air path gives a broader seal that isfeasible with drilled holes. By way of illustration, there are alsoshown two recesses or slots 112 and 113 that intersect the slits 111.With these, the manifold 110 can be quite close to the flaps to beheated, even touching them and still the slots 112 and 113 let the hotair flow freely in a direction which prevents heating of undesired flapareas. Horizontal slots may be used in staggered formations, and variousother opening patterns may be used. A single heater may be attached tothe single fitting 114 of the manifold 110.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

I claim:

1. Heat sealing apparatus for closure of paperboard package flaps havingheat-sealable coatings, including in combination:

a hot air manifold having two surfaces meeting and terminating at asharp acute angle, each surface having at least one row of openingstherealong for sending hot air against. two flap surfaces facings and onopposite sides of said manifold,

at least one air heater connected to said manifold for supplying hot airthereto, each heater comprising an outer metal tubular housing havingfirst and second closed ends and a tangential air inlet near said firstclosed end, an intermediate tubular metal shell inside and spaced fromsaid outer housing except at said closed ends and supported at saidclosed ends to keep the spacing constant and having near said secondclosed end tangential aperture means and closed at both its ends, and aceramic heater body having an inner shell on its outer surface lyinginside and spaced from said intermediate shell, said ceramic heater bodyhaving a plurality of lengthwise passages each with a heating elementinside said passages leading through an outlet larger than the totalcross-sectional area of said lengthwise passages into said manifold atone end and said body stopping short of the closed end of saidintermediate shell at the other end, whereby air enters said tangentialinlet, swirls around in a passage between said housing and saidintermediate shell, flows through said aperture means, swirls toward theother end in a psssage between said intermediate and inner shells andthen flows back through said lengthwise passages and into said manifoldat relatively low velocity and issues from said manifold openings atrelatively low velocity, said manifold openings having a total areagreater than the cross-sectional area of said lengthwise passages,

means for supplying air under pressure to said inlet of said air heater,

means for moving said package relative to said manifold,

means for guiding said flaps as said package is moved, to space saidflaps properly from said manifold,

means for forcing said flaps against each other, and

means for holding them against each other until the heated coatingcongeals and seals them together.

2. The heat sealing apparatus of claim 1 wherein said manifold openingsare substantially identical in size and are spaced apart at varyingdistances to obtain substantially the same flow rate through each.

3. The heat sealing apparatus of claim 1 wherein said rows of manifoldopenings are spaced from the vertex of said sharp acute angle atdifferent distances, being spaced so that each row on one surfacecorresponds to a row on the other surface and lies at the same distancerelative to the box flaps, so that when the flaps are brought togethertheir heated areas directly overlie each other.

4. The apparatus of claim 1 wherein said manifold in unpartitioned andhas a plurality of said heaters spaced apart from each other along saidmanifold to augment the flow and keep it even.

5. The apparatus of claim 1, wherein said manifold has a shape that isgenerally triangular in cross section, with a vertical rear wallconnecting the wall providing said two surfaces and having the airheater connected generally horizontally to said rear wall.

6. The apparatus of claim 1 wherein said manifold has a shape that isgenerally rhomboidal, with a vertical rear wall, a vertical front wallproviding one of said two surfaces and the other walls inclined, theheater lying generally horizontally and leading into said rear wall.

7. The apparatus of claim 1 wherein said means for guiding said flapslies solely outside said flaps, and outside said manifold, only saidmanifold lying between said flaps, said means for guiding acting againstthenatural tendency of said flaps to move apart from each other, saidmeans for guiding being adjustable relative to said manifold forchanging their relative spacing.

8. The apparatus of claim 1 wherein said means for forcing said flapsagainst each other comprises a free running roller engaging an outerflap at a locus spaced from where said outer flap joins the package,'andmoving said outer flap against an inner flap, and a pair of free runningrollers each engaging package walls adjacent said flaps for maintainingpackage shape.

9. The apparatus of claim 8 wherein said rollers are hemispherical inshape with the pair of rollers mounted in a plane perpendicular to theplane of the other said roller.

10. The apparatus of claim 1 wherein said means for holding comprises atleast one row ofcylindrical rollers for engaging a said flap and meansfor sending ambient air against the package adjacent said flaps.

ll. Heat-sealing apparatus for closure of paperboard package flapshaving heat-sealable coatings, including in combination:

a hot air manifold having two surfaces meeting at a sharp acute angleand terminating at the vertex of said angle, each surface having atleast one row or openings therealong forsending hot air against two flapsurfaces facing and on opposite sides of said manifold,

at least one air heater connected to said manifold for supplying hot airthereto and comprising an outer metal tubular housing having first andsecond closed ends and tangential air inlet means near one said end, anelectrical heater inside said housing and having electrical heatingelements therein and passages for air to pass through while contactingsaid heating elements, and baffle means separating said heater andhousing to provide at least two passages between them and having meansnear one end enabling flow from one passage to the other, said heaterpassages leading into said manifold at one end at a large openingtending to decrease rather than to increase the air velocity there,whereby air enters said inlet means, swirls around in a passage, betweensaid housing and said baffle means, flows into a second passage, swirlstoward the other end, and eventually flows through said passages intosaid manifold, said manifold openings having a greater total area thanthe total crosssectional area of said heater passages, so that theheated air issues at low velocity from said manifold opening,

means for supplying air to said air inlet means,

means for moving said package relative to said manifold,

means for spacing said flaps properly from said manifold as said packageis moved, and

means for closing said flaps against each other and holding them againsteach other until the heated coating cogeals and seals them together.

12. Heat-sealing apparatus for closure of paperboard package flapshaving heat-scalable coatings, including in combination:

a hot air manifold having two surfaces meeting and terminating at asharp acute angle, each surface having at least one row of openingstherealong for sending hot air at low velocity and large volume againsttwo flap surfaces facing and on opposite sides of said manifold,

at least one air heater having air passage means therethrough andconnected to said manifold for supplying hot air thereto, the total areaof said manifold openings being substantially larger than the totalcross-sectional area of said air passage means of said heater so as toemit air at lower velocity than that of the air through said heater, and

means for spacing said flaps properly from said manifoldas said packageis moved relative to said manifold, and

means for closing said flaps against each other and holding them againsteach other until the heated coating congeals and seals them together.

13. The apparatus of claim 12 wherein said means for closing said flapsagainst each other comprises a free running roller engaging an outerflap at a locus spaced from the edge where the outer flap joins thepackage, and moving said outer flap against an inner flap and a pair offree running rollers each engaging package walls adjacent said flaps formaintaining package shape.

14. The apparatus of claim 13 wherein said rollers are hemispherical inshape with the pair of rollers mounted in a plane perpendicular to theplane of the other said roller.

15. The apparatus of claim 12 having means for holding said flapsagainst each other until the heat-scalable coating congeals, said meansfor holding comprising at least one row of cylindrical rollers forengaging a said flap and means for sending ambient air against thepackage adjacent said flaps.

16. A method for heat-sealing two pieces of paperboard, at least one ofwhich has been coated with heatsealable coating, comprising moving thetwo pieces at the same velocity,

bringing the two moving pieces into proximity generally opposite eachother, heating a controlled narrow area of each piece by air only, byimpinging on each moving piece a highvolume stream of low-velocity hotair along said controlled narrow area, while limiting the airimpingement and heating to a small fraction of the total width of eachsaid piece, thereby intensively heating a critical strip of the surfaceof each piece above the sealing temperature for said coating,

immediately thereafter forcing the two moving pieces together with theirheated strip surfaces against each other, to close them into sealingposition, and

holding them together under pressure as they move until they cool belowthe sealing temperature of the coating, said pieces being brough intoproximity along two planes that diverge from a vertex at a sharp acuteangle, said strips being spaced the same distance from said vertex, thepressure to hold the pieces together being applied as a gentle rollingpressure at many separated points while sending ambient air against saidpieces in between said separated points, to cool said pieces.

17. A method for heat-sealing two flaps of a paperboard carton, at leastone of which has been coated with heat-scalable coating, comprisingbringing the flaps into proximity along two planes diverging from avertex at a sharp acute angle, heating a controlled narrow area of eachflap as the sole heating of said flaps by impinging on each flat ahigh-volume, low-velocity, strip-shaped stream of very hot air alongsaid controlled narrow area spaced the same distance from said vertex,while limiting at all times the air impingement and heating to a smallfraction of the length and total distance from said vertex to the outeredge of the flap, thereby heating a critical strip of each flap abovethe temperature making said coating tacky,

immediately thereafter forcing the two flaps together, to close theminto sealing position, and

holding them together under pressure until they cool below thecongealing temperature of the coating, the holding step beingaccomplished by constantly applying rolling pressure at a series ofseparated points while applying ambient cooling air to cool the flaps,in between said points.

18. A method for heat sealing two pieces of paperboard, at least one ofwhich has been coated with heat sealable coating, comprising bringingthe two pieces into proximity generally opposite each other,

simultaneously moving the pieces relative to a duct means positionedtherebetween, maintaining at least one of the pieces spaced from and outof contact with said duct means,

heating a portion of each of said surfaces solely by heated gassuccessively impinging hot gas from said duct means at low velocity butof a volume and temperature to raise the coating above the scalabletemperature onto small fractional and equal areas of said surfacesduring their movement relative to the duct means, said areas lying alonga narrow strip constituting a small fraction of the width of each piece,

forcing the pieces together with their heated strip surfaces againsteach other to close them into sealing position immediately after theareas along said strip have been heated, and while they are moving pasta station, applying pressure at said station against successive mutuallyexclusive small fractional areas of the pieces, and while moving holdingthem under pressure on a line substantially normal to their direction ofmovement while directing cooling air against said pieces until they coolbelow the sealing temperature of the coating.

19. The method of claim 18 wherein the pieces are the flaps of a cartonwhich extend from opposite walls thereof,

and the step of bringing the two pieces together comprises folding theflaps into proximity along two planes diverging from a vertex at a sharpangle to provide inner and outer flaps which tend to unfold.

UNITED STATES PATENT OFFICE (IERTIF'ICATE OF CORRECTION Patent No. 777 8Dated December 11, 1973 Inventor) William J. Howe It is certified thaterror appears in the above-identified patent and that said 'LettersPatent are hereby corrected as shown below:

Column 4, line 19, cancel "1,", second occurrence. Column 9, line 67,"one row or" should read one row of Signed and sealed Fhis 17th day ofSeptember 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. ;C; MARSHALL DANN Attesting Officer Commissioner ofPatents F "1M po-wso (10-69) USCOMM-DC 60376P69 5. GOVERNMENT PRINTINGOFFICE I909 O- Si6-3J|,

1. Heat sealing apparatus for closure of paperboard package flaps havingheat-sealable coatings, including in combination: a hot air manifoldhaving two surfaces meeting and terminating at a sharp acute angle, eachsurface having at least one row of openings therealong for sending hotair against two flap surfaces facings and on opposite sides of saidmanifold, at least one air heater connected to said manifold forsupplying hot air thereto, each heater cOmprising an outer metal tubularhousing having first and second closed ends and a tangential air inletnear said first closed end, an intermediate tubular metal shell insideand spaced from said outer housing except at said closed ends andsupported at said closed ends to keep the spacing constant and havingnear said second closed end tangential aperture means and closed at bothits ends, and a ceramic heater body having an inner shell on its outersurface lying inside and spaced from said intermediate shell, saidceramic heater body having a plurality of lengthwise passages each witha heating element inside said passages leading through an outlet largerthan the total cross-sectional area of said lengthwise passages intosaid manifold at one end and said body stopping short of the closed endof said intermediate shell at the other end, whereby air enters saidtangential inlet, swirls around in a passage between said housing andsaid intermediate shell, flows through said aperture means, swirlstoward the other end in a psssage between said intermediate and innershells and then flows back through said lengthwise passages and intosaid manifold at relatively low velocity and issues from said manifoldopenings at relatively low velocity, said manifold openings having atotal area greater than the cross-sectional area of said lengthwisepassages, means for supplying air under pressure to said inlet of saidair heater, means for moving said package relative to said manifold,means for guiding said flaps as said package is moved, to space saidflaps properly from said manifold, means for forcing said flaps againsteach other, and means for holding them against each other until theheated coating congeals and seals them together.
 2. The heat sealingapparatus of claim 1 wherein said manifold openings are substantiallyidentical in size and are spaced apart at varying distances to obtainsubstantially the same flow rate through each.
 3. The heat sealingapparatus of claim 1 wherein said rows of manifold openings are spacedfrom the vertex of said sharp acute angle at different distances, beingspaced so that each row on one surface corresponds to a row on the othersurface and lies at the same distance relative to the box flaps, so thatwhen the flaps are brought together their heated areas directly overlieeach other.
 4. The apparatus of claim 1 wherein said manifold inunpartitioned and has a plurality of said heaters spaced apart from eachother along said manifold to augment the flow and keep it even.
 5. Theapparatus of claim 1, wherein said manifold has a shape that isgenerally triangular in cross section, with a vertical rear wallconnecting the wall providing said two surfaces and having the airheater connected generally horizontally to said rear wall.
 6. Theapparatus of claim 1 wherein said manifold has a shape that is generallyrhomboidal, with a vertical rear wall, a vertical front wall providingone of said two surfaces and the other walls inclined, the heater lyinggenerally horizontally and leading into said rear wall.
 7. The apparatusof claim 1 wherein said means for guiding said flaps lies solely outsidesaid flaps, and outside said manifold, only said manifold lying betweensaid flaps, said means for guiding acting against the natural tendencyof said flaps to move apart from each other, said means for guidingbeing adjustable relative to said manifold for changing their relativespacing.
 8. The apparatus of claim 1 wherein said means for forcing saidflaps against each other comprises a free running roller engaging anouter flap at a locus spaced from where said outer flap joins thepackage, and moving said outer flap against an inner flap, and a pair offree running rollers each engaging package walls adjacent said flaps formaintaining package shape.
 9. The apparatus of claim 8 wherein saidrollers are hemispherical in shape with the pair of rollers mounted in aplane perpendicular to the plane of the other said Roller.
 10. Theapparatus of claim 1 wherein said means for holding comprises at leastone row of cylindrical rollers for engaging a said flap and means forsending ambient air against the package adjacent said flaps. 11.Heat-sealing apparatus for closure of paperboard package flaps havingheat-sealable coatings, including in combination: a hot air manifoldhaving two surfaces meeting at a sharp acute angle and terminating atthe vertex of said angle, each surface having at least one row oropenings therealong for sending hot air against two flap surfaces facingand on opposite sides of said manifold, at least one air heaterconnected to said manifold for supplying hot air thereto and comprisingan outer metal tubular housing having first and second closed ends andtangential air inlet means near one said end, an electrical heaterinside said housing and having electrical heating elements therein andpassages for air to pass through while contacting said heating elements,and baffle means separating said heater and housing to provide at leasttwo passages between them and having means near one end enabling flowfrom one passage to the other, said heater passages leading into saidmanifold at one end at a large opening tending to decrease rather thanto increase the air velocity there, whereby air enters said inlet means,swirls around in a passage, between said housing and said baffle means,flows into a second passage, swirls toward the other end, and eventuallyflows through said passages into said manifold, said manifold openingshaving a greater total area than the total cross-sectional area of saidheater passages, so that the heated air issues at low velocity from saidmanifold opening, means for supplying air to said air inlet means, meansfor moving said package relative to said manifold, means for spacingsaid flaps properly from said manifold as said package is moved, andmeans for closing said flaps against each other and holding them againsteach other until the heated coating cogeals and seals them together. 12.Heat-sealing apparatus for closure of paperboard package flaps havingheat-sealable coatings, including in combination: a hot air manifoldhaving two surfaces meeting and terminating at a sharp acute angle, eachsurface having at least one row of openings therealong for sending hotair at low velocity and large volume against two flap surfaces facingand on opposite sides of said manifold, at least one air heater havingair passage means therethrough and connected to said manifold forsupplying hot air thereto, the total area of said manifold openingsbeing substantially larger than the total cross-sectional area of saidair passage means of said heater so as to emit air at lower velocitythan that of the air through said heater, and means for spacing saidflaps properly from said mani-fold as said package is moved relative tosaid manifold, and means for closing said flaps against each other andholding them against each other until the heated coating congeals andseals them together.
 13. The apparatus of claim 12 wherein said meansfor closing said flaps against each other comprises a free runningroller engaging an outer flap at a locus spaced from the edge where theouter flap joins the package, and moving said outer flap against aninner flap and a pair of free running rollers each engaging packagewalls adjacent said flaps for maintaining package shape.
 14. Theapparatus of claim 13 wherein said rollers are hemispherical in shapewith the pair of rollers mounted in a plane perpendicular to the planeof the other said roller.
 15. The apparatus of claim 12 having means forholding said flaps against each other until the heat-sealable coatingcongeals, said means for holding comprising at least one row ofcylindrical rollers for engaging a said flap and means for sendingambient air against the package adjacent said flaps.
 16. A method forheat-sealing two pieces of paperboard, at least one of which has beencoated with heat-sealable coating, comprising moving the two pieces atthe same velocity, bringing the two moving pieces into proximitygenerally opposite each other, heating a controlled narrow area of eachpiece by air only, by impinging on each moving piece a high-volumestream of low-velocity hot air along said controlled narrow area, whilelimiting the air impingement and heating to a small fraction of thetotal width of each said piece, thereby intensively heating a criticalstrip of the surface of each piece above the sealing temperature forsaid coating, immediately thereafter forcing the two moving piecestogether with their heated strip surfaces against each other, to closethem into sealing position, and holding them together under pressure asthey move until they cool below the sealing temperature of the coating,said pieces being brough into proximity along two planes that divergefrom a vertex at a sharp acute angle, said strips being spaced the samedistance from said vertex, the pressure to hold the pieces togetherbeing applied as a gentle rolling pressure at many separated pointswhile sending ambient air against said pieces in between said separatedpoints, to cool said pieces.
 17. A method for heat-sealing two flaps ofa paperboard carton, at least one of which has been coated withheat-sealable coating, comprising bringing the flaps into proximityalong two planes diverging from a vertex at a sharp acute angle, heatinga controlled narrow area of each flap as the sole heating of said flapsby impinging on each flat a high-volume, low-velocity, strip-shapedstream of very hot air along said controlled narrow area spaced the samedistance from said vertex, while limiting at all times the airimpingement and heating to a small fraction of the length and totaldistance from said vertex to the outer edge of the flap, thereby heatinga critical strip of each flap above the temperature making said coatingtacky, immediately thereafter forcing the two flaps together, to closethem into sealing position, and holding them together under pressureuntil they cool below the congealing temperature of the coating, theholding step being accomplished by constantly applying rolling pressureat a series of separated points while applying ambient cooling air tocool the flaps, in between said points.
 18. A method for heat sealingtwo pieces of paperboard, at least one of which has been coated withheat sealable coating, comprising bringing the two pieces into proximitygenerally op-posite each other, simultaneously moving the piecesrelative to a duct means positioned therebetween, maintaining at leastone of the pieces spaced from and out of contact with said duct means,heating a portion of each of said surfaces solely by heated gassuccessively impinging hot gas from said duct means at low velocity butof a volume and temperature to raise the coating above the sealabletemperature onto small fractional and equal areas of said surfacesduring their movement relative to the duct means, said areas lying alonga narrow strip constituting a small fraction of the width of each piece,forcing the pieces together with their heated strip surfaces againsteach other to close them into sealing position immediately after theareas along said strip have been heated, and while they are moving pasta station, applying pressure at said station against successive mutuallyexclusive small fractional areas of the pieces, and while moving holdingthem under pressure on a line substantially normal to their direction ofmovement while directing cooling air against said pieces until they coolbelow the sealing temperature of the coating.
 19. The method of claim 18wherein the pieces are the flaps of a carton which extend from oppositewalls thereof, and the step of bringing the two pieces togethercomprises folding the flaps into proximity along two planes divergingfrom a vertex at a sharp angle to provide inner and outer flaps whichtend to unfold.